1. Field of the Invention
The present invention relates to a refractive index distribution measuring method and a refractive index distribution measuring apparatus.
2. Description of the Related Art
Japanese Patent Laid-Open No. (“JP”) 01-316627 proposes a method for finding a refractive index distribution of an object by measuring its transmitted wavefront while the object is immersed in a medium (matching oil) which has approximately the same refractive index as that of the object. JP 02-008726 proposes a method for finding a refractive index distribution of an object by measuring its transmitted wavefront while the object is immersed in each of two types of matching oils, which has a slightly different refractive index from that of the object.
These methods disclosed in JPs 01-316627 and 02-008726 need matching oils each of which has approximately the same refractive index as that of the object. However, the matching oil having a high refractive index has a low transmittance, and a detector can output only a weak signal. Thus, the measuring precision of the object having a high refractive index is likely to lower.